Certain polymers which are capable of forming an anisotropic melt phase have been discussed in the technical literature in the past. These polymers sometimes are termed thermotropic liquid crystalline polymers.
Commonly assigned U.S. Pat. No. 4,184,996 to Calundann discloses an anisotropic melt-forming polyester consisting essentially of 4-oxybenzoyl units, 2,6-dioxynaphthalene units and terephthaloyl units in specified concentrations. 6-oxy-2-naphthoyl units are not included. The possible presence of dicarboxy and dioxy units is mentioned at Col. 4, lines 17 and 24. The resulting polymer has been found to exhibit a relatively high melt viscosity which has precluded the achievement of a relatively high degree of polymerization in the melt phase. Accordingly, it has been found essential to employ a subsequent solid state polymerization as indicated in Example II of that patent if one is to substantially increase the molecular weight of the product. Such relatively high melt viscosity also has rendered somewhat difficult the melt extrusion of filaments of relatively low denier, and the molding of shaped articles having complex configurations or relatively thin cross-sections.
Commonly assigned U.S. Pat. No. 4,219,461 to Calundann discloses an anisotropic melt-forming polyester consisting essentially of 6-oxy-2-naphthoyl units, 4-oxybenzoyl units, symmetrical dioxy aryl units, and symmetrical dicarboxy aryl units in specified concentrations. In all instances the relatively expensive 6-oxy-2-naphthoyl units are present in concentrations of 20 to 40 mole percent. The polyester of the present invention commonly exhibits higher as-spun fiber moduli, a better retention of properties at elevated temperatures (e.g., 200.degree. C.), and a higher heat deflection temperature than the polyester of U.S. Pat. No. 4,219,461.
Our commonly assigned U.S. Pat. No. 4,473,682 discloses an anisotropic melt-forming polyester consisting essentially of 6-oxy-2-naphthoyl units, 4-oxybenzoyl units, 4,4'-dioxybiphenyl units, and terephthaloyl units. The polyester of the present invention commonly exhibits a higher heat deflection temperature, better mechanical properties, and the ability to be molded at lower temperatures than the polyester of U.S. Pat. No. 4,473,682.
U.S. Pat. No. 4,370,466 to Siemionko discloses an anisotropic melt-forming polyester consisting essentially of 6-oxy-2-naphthoyl units, 4-oxybenzoyl units, 1,4-dioxyphenylene units, and isophthaloyl units. The polyester of the present invention commonly exhibits better hydrolytic stability, and a better retention of properties at elevated temperatures (e.g., 200.degree. C.) than the polyester of U.S. Pat. No. 4,370,466.
Commonly assigned U.S. Pat. No. 4,256,624 to Calundann discloses an anisotropic melt-forming polyester consisting essentially of 6-oxy-2-naphthoyl units, symmetrical dioxy aryl units, and symmetrical dicarboxy aryl units in specified concentrations. At Col. 6, lines 19 to 24, it is stated that 10 mole percent or less of 4-oxybenzoyl units optionally can be present. The polyester of the present invention commonly exhibits a higher heat deflection temperature, and can be formed on a more economical basis than the polyester of U.S. Pat. No. 4,256,624.
U.S. Pat. No. 4,188,476 to Irwin discloses an anisotropic melt-forming polyester consisting essentially of 4-oxybenzoyl units, 2,6-dioxynaphthalene units, terephthaloyl units, and isophthaloyl units or 3-oxybenzoyl units. The polyester of the present invention commonly exhibits higher as-spun fiber properties than the polyester of U.S. Pat. No. 4,188,476.
Commonly assigned U.S. Pat. No. 4,351,918 to Charbonneau et al discloses an anisotropic melt-forming polyester-amide which consists essentially of 6-oxy-2-naphthoyl units, 4-oxybenzoyl units, terephthaloyl units, and amide units. The polyester of the present invention commonly exhibits a higher heat deflection temperature and can be formed on a more economical basis than the polyester of U.S. Pat. No. 4,351,918.
It is an object of the present invention to provide an improved melt processable polyester which forms a readily tractable anisotropic melt phase which facilitates polymerization in the melt to a relatively high inherent viscosity in a satisfactory yield.
It is an object of the present invention to provide a novel melt processable polyester which forms an anisotropic melt phase and which has been found to be capable of melt extrusion to form quality high performance fibers, films, three-dimensional molded articles, etc. using standard equipment.
It is an object of the present invention to provide a novel polyester which forms a readily melt processable anisotropic melt phase below approximately 325.degree. C.
It is an object of the present invention to provide a novel improved polyester which can be more readily melt processed than the polyester of U.S. Pat. No. 4,184,996.
It is another object of the present invention to provide a novel polyester which can be melt processed to form articles which exhibit a superior retention of mechanical properties when heated from room temperature to 200.degree. C.
These and other objects, as well as the scope, nature and utilization of the invention will be apparent to those skilled in the art from the following detailed description and appended claims.